The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
Tadeusz H Dzido - One of the best experts on this subject based on the ideXlab platform.
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thin layer Chromatogram development with a moving pipette delivering the mobile phase onto the surface of the adsorbent layer
Journal of Chromatography A, 2018Co-Authors: Aneta Halkagrysinska, Kamila Skop, Anna Klimekturek, Marta Gorzkowska, Tadeusz H DzidoAbstract:Abstract The new approach to the development of thin-layer Chromatograms is presented. For the first time we show flexible mobile phase dosage onto the surface of the adsorbent layer by moving pipette combined with precise syringe pumps. The pipette is driven into movement by computer controlled 3D machine (modified 3D printer mechanism). Delivery of the mobile phase to the adsorbent layer is equal to or lower than that of conventional development. Therefore Chromatograms can be developed with optimal mobile phase velocity, adjusted to its absorption rate by the adsorbent layer. Under such conditions there is no excess of eluent on the surface of the adsorbent layer so higher performance of the chromatographic system can be obtained. Moreover Chromatograms can be developed with constant linear mobile phase velocity and therefore the relationships the plate height vs. mobile phase linear velocity obtained with planar chromatography driven by capillary forces are investigated and reported. In addition the contribution of starting spot variance in total peak variance and the influence of narrowing of starting spots on performance of the chromatographic system have been studied. The results confirm a very significant starting spot variance contribution to total peak variance and consequently considerable influence of starting spot size on plate height of the separation system, when Chromatogram is developed on a short distance. In the paper the advantages and disadvantages of the prototype device and its possible application are discussed.
Aneta Halkagrysinska - One of the best experts on this subject based on the ideXlab platform.
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thin layer Chromatogram development with a moving pipette delivering the mobile phase onto the surface of the adsorbent layer
Journal of Chromatography A, 2018Co-Authors: Aneta Halkagrysinska, Kamila Skop, Anna Klimekturek, Marta Gorzkowska, Tadeusz H DzidoAbstract:Abstract The new approach to the development of thin-layer Chromatograms is presented. For the first time we show flexible mobile phase dosage onto the surface of the adsorbent layer by moving pipette combined with precise syringe pumps. The pipette is driven into movement by computer controlled 3D machine (modified 3D printer mechanism). Delivery of the mobile phase to the adsorbent layer is equal to or lower than that of conventional development. Therefore Chromatograms can be developed with optimal mobile phase velocity, adjusted to its absorption rate by the adsorbent layer. Under such conditions there is no excess of eluent on the surface of the adsorbent layer so higher performance of the chromatographic system can be obtained. Moreover Chromatograms can be developed with constant linear mobile phase velocity and therefore the relationships the plate height vs. mobile phase linear velocity obtained with planar chromatography driven by capillary forces are investigated and reported. In addition the contribution of starting spot variance in total peak variance and the influence of narrowing of starting spots on performance of the chromatographic system have been studied. The results confirm a very significant starting spot variance contribution to total peak variance and consequently considerable influence of starting spot size on plate height of the separation system, when Chromatogram is developed on a short distance. In the paper the advantages and disadvantages of the prototype device and its possible application are discussed.
Jose R Tormo - One of the best experts on this subject based on the ideXlab platform.
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HPLC studio: a novel software utility to perform HPLC Chromatogram comparison for screening purposes.
Journal of biomolecular screening, 2003Co-Authors: J B García, Jose R TormoAbstract:A new tool, HPLC Studio, was developed for the comparison of high-performance liquid chromatography (HPLC) Chromatograms from microbial extracts. The new utility makes it possible to create a virtual Chromatogram by mixing up to 20 individual Chromatograms. The virtual Chromatogram is the first step in establishing a ranking of the microbial fermentation conditions based on either the area or diversity of HPLC peaks. The utility was used to maximize the diversity of secondary metabolites tested from a microorganism and therefore increase the chances of finding new lead compounds in a drug discovery program.
Robert E Synovec - One of the best experts on this subject based on the ideXlab platform.
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high speed peak matching algorithm for retention time alignment of gas chromatographic data for chemometric analysis
Journal of Chromatography A, 2003Co-Authors: Kevin J. Johnson, Bob W Wright, Kristin H Jarman, Robert E SynovecAbstract:A rapid retention time alignment algorithm was developed as a preprocessing utility to be used prior to chemometric analysis of large datasets of diesel fuel profiles obtained using gas chromatography (GC). Retention time variation from Chromatogram-to-Chromatogram has been a significant impediment against the use of chemometric techniques in the analysis of chromatographic data due to the inability of current chemometric techniques to correctly model information that shifts from variable to variable within a dataset. The alignment algorithm developed is shown to increase the efficacy of pattern recognition methods applied to diesel fuel Chromatograms by retaining chemical selectivity while reducing Chromatogram-to-Chromatogram retention time variations and to do so on a time scale that makes analysis of large sets of chromatographic data practical. Two sets of diesel fuel gas Chromatograms were studied using the novel alignment algorithm followed by principal component analysis (PCA). In the first study, retention times for corresponding chromatographic peaks in 60 Chromatograms varied by as much as 300 ms between Chromatograms before alignment. In the second study of 42 Chromatograms, the retention time shifting exhibited was on the order of 10 s between corresponding chromatographic peaks, and required a coarse retention time correction prior to alignment with the algorithm. In both cases, an increase in retention time precision afforded by the algorithm was clearly visible in plots of overlaid Chromatograms before and then after applying the retention time alignment algorithm. Using the alignment algorithm, the standard deviation for corresponding peak retention times following alignment was 17 ms throughout a given Chromatogram, corresponding to a relative standard deviation of 0.003% at an average retention time of 8 min. This level of retention time precision is a 5-fold improvement over the retention time precision initially provided by a state-of-the-art GC instrument equipped with electronic pressure control and was critical to the performance of the chemometric analysis. This increase in retention time precision does not come at the expense of chemical selectivity, since the PCA results suggest that essentially all of the chemical selectivity is preserved. Cluster resolution between dissimilar groups of diesel fuel Chromatograms in a two-dimensional scores space generated with PCA is shown to substantially increase after alignment. The alignment method is robust against missing or extra peaks relative to a target Chromatogram used in the alignment, and operates at high speed, requiring roughly 1 s of computation time per GC Chromatogram.
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analysis of unresolved Chromatograms by the absorbance ratio and sequential Chromatogram ratio techniques coupled with peak suppression
Journal of Chromatography A, 1994Co-Authors: Timothy J Bahowick, Darren R Dunphy, Robert E SynovecAbstract:Abstract The sequential Chromatogram ratio (SCR) technique was successively applied or was coupled with the absorbance ratio (AR) technique to facilitate analysis of a peak of interest that was overlapped with two other peaks. First, the AR or SCR technique was used to suppress one undesired peak. This created or elongated a region of pure-component elution for the peak of interest. Then the appropriate ratio technique was applied to this region for qualitative and quantitative analysis. The AR technique allows suppression and qualitative analysis of unknown components via the absorptivity ratio. For the SCR technique, peak identity can be deduced prior to suppression and quantitative analysis. A statistical peak matching procedure that employs user-selected standards is described for the SCR technique, by which components in sequentially injected samples may be identified based on differences in retention time, tR, or in diffusion coefficient, Dm, which controls peak width. For two similarly retained analytes in sequentially injected samples, having a factor-of-two difference in Dm, the problem of reduced resolution, Rs, with a third peak was investigated by manipulating the data to simulate a reduction in selectivity factor. Below a limit, Rs = 0.38, the original two analytes could no longer be qualitatively distinguished. At this same Rs limit, the two-times difference in Dm, for two analytes having essentially zero tR-based resolution, provided equivalent qualitative discrimination of peaks as a tR-based resolution of 0.12 for two analytes having equal Dm. The classical problems of inaccurate baseline correction and run-to-run retention variation were examined, and the latter was more limiting for the SCR technique. Still, small tR shifts were adequately corrected by selecting and aligning a common peak in sequential Chromatograms.
Ten Feizi - One of the best experts on this subject based on the ideXlab platform.
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high affinity binding of the leucocyte adhesion molecule l selectin to 3 sulphated lea and lex oligosaccharides and the predominance of sulphate in this interaction demonstrated by binding studies with a series of lipid linked oligosaccharides
Biochemical and Biophysical Research Communications, 1992Co-Authors: Paula J Green, Mitsunori Kiso, Chunting Yuen, M S Stoll, Takuya Tamatani, Masayuki Miyasaka, Tomoyuki Watanabe, Akira Hasegawa, Ten FeiziAbstract:Abstract The binding of the leucocyte adhesion molecule L-selectin has been investigated toward several structurally defined lipid-linked oligosaccharides immobilized on silica gel Chromatograms or plastic wells. In both assay systems the 3′-sulphated Le a /Le x type tetrasaccharides were more strongly bound than 3′-sialyl analogues. A considerable binding was observed to the 3′-sulphated oligosaccharide backbone in the absence of fucose but not to a 3′-sialyl analogue or fuco-oligosaccharide analogues lacking sulphate or sialic acid. Affinity for other sulphated saccharides: 3′-sulphoglucuronyl neolactotetraosyl ceramide and glycolipids with sulphate 3′-linked to terminal or sub-terminal galactose or N-acetylgalactosamine was detected in the Chromatogram assay only. These studies, together with earlier reports that L-selectin binding to endothelium is inhibited by sulphatide, highlight the relative importance of sulphate in the adhesive specificity of this protein.